US Department of HHS, Centers for Disease Control and Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, “no name,” November 24, 2015.

PrEP as an HIV Biomedical Prevention Strategy

Gay, bisexual, and other men who have sex with men (MSM) account for 66% of all new HIV infections in the U.S. each year [1]. The number of new HIV infections among MSM increased 12% between 2008 and 2010 in the U.S., with a sharper 22% increase among MSM 13 – 24 years of age [1]. Such disparities in the HIV epidemic show the urgent need to develop new ways to prevent HIV infection among this population. Daily oral pre-exposure prophylaxis (PrEP) is a promising biomedical HIV prevention strategy recommended by the CDC for those at high risk of HIV, including MSM [2].

PrEP Awareness and Uptake

Among MSM in the U.S., PrEP awareness is increasing, and interest in and willingness to use PrEP are high [3, 4]. Despite high acceptability of PrEP, uptake among MSM is low, often less than 7% in many studies [4-6]. Reasons for low PrEP uptake among MSM include concerns about cost, the burden of daily dosing, and worry about long-term side effects [4, 7, 8].

PrEP Adherence

Adherence to a daily pill has been important for best efficacy in PrEP clinical trials. Across major PrEP trials, greater adherence to daily oral PrEP was associated with greater HIV protection [9 -11]. For example, the iPrEx study showed fewer HIV infections among MSM with higher adherence [11]. In contrast, no HIV protection was found in two trials, VOICE [9] and FEM-PrEP [10], in which PrEP adherence was very low.

Alternatives to daily oral pill-taking which could promote PrEP adherence and be easily implemented in clinical and community settings are needed. Current investigations of other delivery options include long-acting injectable antiretroviral (ARV) drugs [12], and implants with sustained release of ARVs [13]. At the 2016 Conference on Retroviruses and Opportunistic Infections, over a dozen abstracts focused on long-acting and sustained delivery PrEP options. For example, the ÉCLAIR Phase 2a randomized, double-blinded study [14] evaluated intramuscular injections for PrEP in a sample of 126 men (83% MSM). The study found that the medication was well tolerated over 41 weeks and the majority of participants reported satisfaction with the injections.

At Northwestern University, the Sustained Long-Acting Protection Against HIV (SLAP HIV) program aims to develop and test a PrEP implant to provide HIV protection for up to a year at a time. SLAP HIV is funded by the National Institute of Allergy and Infectious Diseases and led by Drs. Thomas Hope and Patrick Kiser. Collaborating scientists from multiple institutions are developing two additional drug delivery systems, including injectable PrEP. These lines of research indicate that sustained release or long-acting agents are attractive alternatives for use of PrEP. They avoid the need for high adherence to daily oral regimens which limit the effectiveness of PrEP as a prevention strategy [12, 13].

[5] Rucinski, K. B., Mensah, N. P., Sepkowitz, K. A., Cutler, B. H., Sweeney, M. M., & Myers, J. E. (2013). Knowledge and use of pre-exposure prophylaxis among an online sample of young men who have sex with men in New York City. AIDS and Behavior, 17(6), 2180-2184. doi: 10.1007/s10461-013-0443-y

[6] Mayer, K. H., Oldenburg, C., Novak, D. S., Krakower, D., & Mimiaga, M. J. (2014). Differences in PrEP knowledge and use in US MSM users of a popular sexual networking site surveyed in August 2013 and January 2014. AIDS Research and Human Retroviruses, 30(S1), A91-A92. doi:10.1089/aid.2014.5168a.abstract